Method of agitating molten metal in a metal-dispensing furnance

ABSTRACT

A method of agitating molten metal, utilizing a metal-dispensing furnace having a molten metal reservoir, a surge chamber joined to the reservoir by a submerged opening, and a dispensing chamber having a discharge spout and intermittently connected with the surge chamber over a baffle wall separating the surge and dispensing chambers. The surge and dispensing chambers being intermittently exposed to a common source of air or inert gas under pressure, and to a common exhaust so that the molten metal in the dispensing chamber is periodically discharged, while simultaneously molten metal in the surge chamber is caused to backflow into the reservoir, agitating the metal therein, particularly at the bottom of the reservoir; then, alternately, is permitted to refill the surge and dispensing chambers causing further agitation of the molten metal in the reservoir.

United States Patent Division of Ser. No. 664,372, Aug. 30, 1967, Pat. No. 3,510,116 Patented Aug. 17, 1971 METHOD OF AGITATING MOLTEN METAL IN A METAL-DISPENSING FURNANCE 3 Claims, 7 Drawing Figs.

U.S. Cl 222 1, 222/399 Int. Cl GOlf 11/28 Field of Search 222/1 61,

EXHAUST CLOSED Assistant Examiner-Francis J. Bartuska AtmrneyLyon & Lyon ABSTRACT: A method of agitating molten metal, utilizing a metal-dispensing furnace having a molten metal reservoir, a surge chamber joined to the reservoir by a submerged opening, and a dispensing chamber having a discharge spout and intermittently connected with the surge chamber over a baffle wall separating the surge and dispensing chambers.

The surge and dispensing chambers being intermittently exposed to a common source of air or inert gas under pressure, and to a common exhaust so that the molten metal in the dispensing chamber is periodically discharged, while simultaneously molten metal in the surge chamber is caused to backflow into the reservoir, agitating the metal therein, particularly at the bottom of the reservoir; then, alternately, is permitted to refill the surge and dispensing chambers causing further agitation of the molten metal in the reservoir.

CONTROLLER 2 NR OR 9 INERT GAS SUPPLY 2 OPEN sum 1 OF 2 PMENTED AUG] 7 l9?! PATENTED AUG] 7 l87| SHEET 2 BF 2 CONTROLLER INERT GAS SUPPLY CONTROLLER AIR OR INERT GAS SUPPLY 'EXHAUST L U Z MA W 0 j A rroe/vf V5 METHOD OF AGITATING MOLTEN METAL IN A METAL-DISPENSING FURNANCE This application is a division of my copending application, Ser. No. 664, 372, filed Aug. 30, 1967, now U.S. Pat. No. 3,510,116, entitled Metal Dispensing Furnace and Method of Operation.

BACKGROUND AND SUMMARY OF THE INVENTION It is essential in the intermittent dispensing of molten metal alloys into molds of various types including those contained in diecasting machines that the formulation remain constant; that is, for example, heavier components remain uniformly suspended and not settle out. It is also essential that impurities be prevented from discharging with the molten metal, without requiring frequent cleaning of the furnace. Also, it is desirable that the metal in the furnace reservoir have a higher temperature than the metal temperature at the pouring spout.

A primary object of the present invention is to provide an effective method of agitating the molten metal alloy in the reservoir primarily below the surface slag so that the heavier components are maintained in suspension without causing the slag or other surface contaminants from being mixed into the molten metal. This is accomplished by providing a surge chamber between the reservoir and dispensing chamber, the surge chamber preferably being larger than the dispensing chamber, and pressurized simultaneously with pressurization of the dispensing chamber so as to drive rearwardly into the reservoir a quantity of molten metal calculated to cause an optimum stirring and mixing of the metal.

, A search of the prior art did not reveal this concept; how ever, in some instances, backflow did occur but in an amount totally inadequate to effect stirring of the molten metal. Of the references revealed in the search, the following patents are selected as representative: Howard, U.S. Pat. No. 1,138,1l May 1915; Peterson U.S. Pat. No. 2,464,714 Mar. i949; Edstrand, U.S. Pat. No. 3,846,740 Aug. I958; Holz, U.S. Pat. No. 3,050,794 Aug. 1962;.

The Howard patent discloses a glass furnace in which some backflow into the refining chamber occurs. It is clear that the backflow is greatly restricted and not at high velocity. It is clear that this flow was not intended to and, intact, does not accomplish the purposes of the present invention.

The Peterson patent uses a displacement member and the storage" compartment and the melting compartment are in communication above as well as below the liquid level. There is no disclosure regarding the size of the submerged connecting passage, and no comment regarding whether or not any backflow occurs. The overflow lip to the discharge spout is only slightly above liquid level, so that if any inadvertent backflow does occur, it would be ineffectual.

The Edstrand and Holz patents show a dispensing chamber with a constructed vertical tube communicating with the reservoir. As a consequence, the volume of backflow is, at best, only a small fraction of the displacement in the dispensing chamber, so that, at best, no effective agitation of the metal in the reservoir can occur.

A further object of this invention is to provide a method utilizing a novelly related surge chamber and dispensing chamber in which the surge chamber is not only larger than the dispensing chamber, but communicates therewith through restricted passages so that backflow into the reservoir is both rapid and of sufficient volume to effect optimum agitation.

- DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the molten metal furnace, taken principally along the line l-l of FIG. 2.

FIG. 2 is a longitudinal sectional view thereof, taken through 2-2 of FIG. 1, the level of the molten metal being shown in its quiescent state prior to dispensing a charge of molten metal.

FIG. 3 is an enlarged fragmentary sectional view, taken through 3-3 of FIG. 1, showing the restricted entrance slits communicating with the dispensing chamber, and showing the dispensing spout.

FIG. 4 is a similar enlarged fragmentary sectional view, taken through 4-4 of FIG. 1, showing the baffle between the surge and dispensing chambers, and showing the entrance ends of the flow-restricting slits between the surge and dispensing chambers.

FIG. 5 is a similar fragmentary sectional view, showing the opening communicating between the surge chamber and the reservoir.

FIG. 6 is an enlarged fragmentary sectional view, taken within 6-6 of FIG. 2, showing the molten liquid level in the surge chamber and dispensing chamber on completion of the dispensing cycle, and indicating diagrammatically, the means for pressurizing the surge and dispensing chamber.

FIG. 7 is a similar fragmentary sectional view, showing the surge chamber in its refilled condition, and showing the dispensing chamber in the process of being refilled with molten metal.

The method of agitating molten metal utilizes a metaldispensing furnace which is constructed in the usual manner of brick, capable of withstanding the temperatures of molten metal. It is customary to encase the brick in suitable insulating material, which in turn is encased in a metal jacket or, for mechanical protection, suitable metal framework is provided for the brick, the framework being protected by the brick from exposure to the temperatures of the molten metal.

The furnace may be gas or oil tired, or may be an inductionor resistance-type electric furnace. For purposes of illustration, a gas-fired type of furnace is shown. The furnace includes a reservoir 1 for molten metal, the reservoir having a bottom wall 2, sidewalls 3, end walls 4 and S, and a top wall 6 which is arched to provide mechanical support. At one end 4, there is provided a charging extension 7, open at its upper side, and communicating with the reservoir through an opening 8, closed by a vertically adjustable door 9, the lower end of which dips into the molten metal 10, so as to isolate the charging extension 7 from the reservoir 1. If the furnace is of the gas-fired type, a substantial chamber is provided above the surface of the metal intersected by a burner opening 1 1, which receives a gas burner unit, not shown. A vent 12 leads from the reservoir. The construction thus far described may be considered as conventional.

At the end of the reservoir, opposite from the charging extension 7, is a dispensing extension 13. In the exercise of the present invention, the dispensing extension includes an upwardly open surge chamber 14 adjacent the end wall 5, and an upwardly open dispensing chamber 15 separated from the surge chamber 14 by a battle wall 16, the upper surface of which is below the intended minimum level of molten metal.

The submerged portion of the end wall 5 is reduced in width, as indicated by 17, and the reservoir communicates with the surge chamber through a submerged opening 18.

Resting on the baffle 16 and closing the dispensing chamber 15, is a metering block 19, having a set of relatively narrow slots 20 which form with the upper side of the baffle wall 16, a series of restricted passageways communicating between the surge chamber 14 and the dispensing chamber 15. A dispensing spout 21 extends upwardly at an angle from the dispensing chamber 15 to a height slightly above the maximum intended level of metal in the reservoir 1.

The dispensing extension 13 is covered with a suitable deck 22 which may be metal or metal lined with suitable heat-resisting material. The deck forms a sealed closure for the dispensing chamber 15 and a surge chamber 14 so that these chambers may be pressurized.

Connected directly to the surge chamber 14 and indirectly to the dispensing chamber 15 through the slots 20 is a surge line 23 for the flow of air, or, preferably, an inert gas, to or from the chambers. The surge line connects to an exhaust line 14, having an exhaust valve 25, and to a supply line 26 having a supply valve 27 and a throttle valve 28. The supply line 26 connects to a source of air or inert gas under pressure, in-

dicated by 29. The exhaust valve 25 and supply valve 27 are preferably solenoid operated and connected to a controller 39, arranged to open these valves alternately and to time the cycle that each valve is open.

The method of agitating molten metal is as follows:

When the reservoir and chambers are exposed to atmospheric pressure, the operating level of the molten metal may vary between a maximum level just below the discharge level of the spout 21, and a minimum level just above the upper surface of the baffle wall 16. Due to the communication provided between the reservoir and the two chambers, the molten metal fills the reservoir and the two chambers to a common level, as shown in FIG. 2. This is the condition when the exhaust valve 25 is opened. When the exhaust valve is closed and air or inert gas is applied under pressure, the rate of flow of the air or gas is determined by the adjustment of the throttle valve 28. While the slots offer some resistance to the flow of molten metal therethrough, they do not offer appreciable resistance to the flow of a gas. Therefore, once the slots 20 are cleared of metal, the pressure in the dispensing chamber and the surge chamber is equal so that as additional gas is supplied, the levels of these two chambers recede essentially equally. The molten metal in the dispensing chamber discharges through the spout 21, whereas the molten metal in the surge chamber flows backwardly into the reservoir. The backward-flowing metal flows across the bottom of the reservoir agitating the metal therein and in particular, causing a remixing of the heavier constituents of the molten metal alloy. This is accomplished without appreciably disturbing the surface and any slag which may be floating thereon, so that the agitation of the metal does not introduce contamination. It will be noted, as shown in FIG. 1, that the passageway or opening 18 may be disposed at one lateral side of the wall 5, so that the incoming surge of molten metal from the surge chamber 14 may tend to move in a rotary path, as indicated by arrows in FIG. 1. The amount of agitation may be optimized by providing a larger or smaller surge chamber. It is found desirable that the surge chamber be at least as large as the dispensing chamber.

The amount of metal discharged from the spout 21 varies with the capacity of the die or mold cavity intended to receive the metal. For maximum efficiency, however, it is desirable to pour a quantity of metal representing a substantial portion of the capacity ofthe dispensing chamber. This also increases the volume of metal which surges backwardly into the reservoir.

The volume of molten metal discharged with each pressure cycle is determined by the pressure and the time that the dispensing chamber is exposed to the pressure. After the dispensing cycle is completed, the supply valve 27 is closed and the exhaust is opened to atmosphere. lnitially this causes a surge of molten liquid from the reservoir into the surge chamber 14, filling the chamber to a level above the baffle wall 16. The molten metal then flows through the slots 20 into the dispensing chamber. The slots offer some resistance to the flow of the metal so that the dispensing chamber fills at a slower rate than the surge chamber 14. The time required to refill the dispensing chamber is, however, well under the time required to present empty dies or molds to the dispensing spout. By changing the width or the number of slots 20, the flow into the dispensing chamber may be optimumized.

Thus, it will be seen that the method of dispensing and agitating molten metal consists essentially in producing a backward surge of molten metal into the reservoir simultaneously with the dispensing of the molten metal into dies or molds, and then producing a forward surge of molten metal during the initial portion of the cycle in which a new charge of molten metal is brought into readiness for a subsequent dispensing cycle, the volume of metal moved by each surge being such as to produce optimum stirring or agitation of the molten metal, especially the lower portion of the metal in the reservoir.

It is highly desirable to maintain a temperature gradient between the reservoir and the dispensingjehamber; that is, the molten metal in the reservoir should be igher than the metal in the dispensing chamber. This temperature difference can be preselected by the thickness of the wall 17 and the baffle 16 and the selection of the material comprising these walls so as to have a faster or slower rate of heat transfer.

The present embodiment of this invention is to be considered in all respects as illustrative and not restrictive.

We claim:

1. In a metal-dispensing furnace having a reservoir, a surge chamber and dispensing chamber, the surge chamber and reservoir being in communication adjacent their bottom walls and the surge chamber and dispensing chamber being separated by a bafile the level of which is below but adjacent the minimum operating level of molten metal in said reservoir, the method of agitating the metal in said reservoir characterized by:

a. forcing molten metal from said surge chamber in a backward flow along the bottom of said reservoir to agitate the contents thereof;

b. and simultaneously dispensing a charge of molten metal from said dispensing chamber;

c. and alternately filling said surge chamber and dispensing chamber from said reservoir thereby causing a forward flow of molten metal along the bottom ofsaid reservoir.

2. A method of agitating the molten metal contained in a reservoir chamber ofa metal-dispensing furnace in the course of discharging metal therefrom, the furnace having a closed surge chamber in communication with the bottom of the reservoir chamber and dispensing chamber having an outlet spout, said method characterized by:

a. periodically pressurizing the surge chamber to effect simultaneous discharge of molten metal from the outlet port and causing a backflow of metal into the reservoir chamber;

b. and periodically relaxing the pressure in said surge chamber to cause forward flow of metal from said reservoir chamber, whereby the molten metal in said reservoir chamber is agitated by the alternate backward and forward flow of molten metal.

3. A method of agitating molten metal in a molten metal dispensing furnace having a reservoir chamber, a surge chamber and a dispensing chamber separated by walls, the wall separating the reservoir and surge chambers having an opening adjacent the bottoms of the chambers, the wall separating the surge and dispensing chambers having an opening above the level of the opening between the reservoir and surge chambers, the surge chamber being sealed and capable of being pressurized, said agitating method characterized by:

a. applying pressure to the surge chamber to cause backward flow of molten metal from the surge chamber along the bottom of the reservoir chamber to agitate the contents of the reservoir chamber;

b. utilizing the application of pressure to the surge chamber to effect simultaneous supplying of a charge of molten metal to the dispensing chamber for discharge therefrom;

c. alternately releasing the application of pressure to the surge chamber to cause a forward flow of molten metal from the bottom ofthe reservoir chamber into the bottom ofthe surge chamber. 

1. In a metal-dispensing furnace having a reservoir, a surge chamber and dispensing chamber, the surge chamber and reservoir being in communication adjacent their bottom walls and the surge chamber and dispensing chamber being separated by a baffle the level of which is below but adjacent the minimum operating level of molten metal in said reservoir, the method of agitating the metal in said reservoir characterized by: a. forcing molten metal from said surge chamber in a backward flow along the bottom of said reservoir to agitate the contents thereof; b. and simultaneously dispensing a charge of molten metal from said dispensing chamber; c. and alternately filling said surge chamber and dispensing chamber from said reservoir thereby causing a forward flow of molten metal along the bottom of said reservoir.
 2. A method of agitating the molten metal contained in a reservoir chamber of a metal-dispensing furnace in the course of discharging metal therefrom, the furnace having a closed surge chamber in communication with the bottom of the reservoir chamber and dispensing chamber having an outlet spout, said method characterized by: a. periodically pressurizing the surge chamber to effect simultaneous discharge of molten metal from the outlet port and causing a backflow of metal into the reservoir chamber; b. and periodically relaxing the pressure in said surge chamber to cause forward flow of metal from said reservoir chamber, whereby the molten metal in said reservoir chamber is agitated by the alternate backward and forward flow of molten metal.
 3. A method of agitating molten metal in a molten metal dispensing furnace having a reservoir chamber, a surge chamber and a dispensing chamber Separated by walls, the wall separating the reservoir and surge chambers having an opening adjacent the bottoms of the chambers, the wall separating the surge and dispensing chambers having an opening above the level of the opening between the reservoir and surge chambers, the surge chamber being sealed and capable of being pressurized, said agitating method characterized by: a. applying pressure to the surge chamber to cause backward flow of molten metal from the surge chamber along the bottom of the reservoir chamber to agitate the contents of the reservoir chamber; b. utilizing the application of pressure to the surge chamber to effect simultaneous supplying of a charge of molten metal to the dispensing chamber for discharge therefrom; c. alternately releasing the application of pressure to the surge chamber to cause a forward flow of molten metal from the bottom of the reservoir chamber into the bottom of the surge chamber. 